KR101477801B1 - Crystallization processes for producing bisphenols - Google Patents

Abstract

A method for making Bisphenol A (BPA) with a purity of more than 99.7% by (a) reacting phenol and acetone using an acid catalyst, (b) separating a BPA-phenol adduct by crystallisation and (c) removing phenol from the adduct, in which (b) involves continuous suspension crystallisation with a total dwell time of more than 4 hours in at least 3 crystallisers, by cooling first to 50-70[deg] C in two parallel crystallisers and then to 40-50[deg] C in a third crystalliser connected in series with the first two. A method for the production of Bisphenol A (BPA) with a purity of more than 99.7%, by (a) reacting phenol with acetone in presence of an acid catalyst, (b) separating a BPA-phenol adduct from the product mixture by crystallisation, filtration and washing, and (c) removing the phenol from the adduct, in which stage (b) involves continuous suspension crystallisation in at least three crystallisers connected in such a way that the mixture is first cooled to 50-70[deg] C in two crystallisers in parallel and then cooled to 40-50[deg] C in a third crystalliser in series with the first two, the total residence time of the mixture over all crystallisers being more than 4 hours.

Description

[0001] CRYSTALLIZATION PROCESSES FOR PRODUCING BISPHENOLS [0002]

Bisphenols as condensation products of phenol and carbonyl compounds are starting materials or intermediates for the preparation of various products. Particularly, condensation products produced in the reaction between phenol and acetone, i.e., 2,2-bis (4-hydroxyphenyl) propane (i.e., bisphenol A or "BPA") are industrially important. BPA can be used as a starting material for the preparation of various polymeric materials such as polyacrylates, polyetherimides and modified phenol formaldehyde resins. A preferred field of application of BPA as a starting material involves the preparation of epoxy resins and polycarbonates.

Methods for the synthesis of bisphenol A (BPA) by ion exchange catalysis are disclosed, for example, in U.S. Patent No. 4,391,997, U.S. Patent No. 4,400,555, U.S. Patent No. 4,590,303, and European Patent Application No. 0210366A. It is also known to produce BPA on a large scale by passing a mixture of phenol and acetone through a fixed bed reactor packed with a polystyrene sulfonic acid ion exchanger resin and post-treating it.

The reaction of phenol with acetone in the presence of an acidic catalyst produces a product mixture (reaction mixture) which can contain mainly BPA and water, in addition to unreacted phenol and possibly also acetone. Also, typical byproducts (subcomponents) of the condensation reaction such as 2- (4-hydroxyphenyl) -2- (2-hydroxyphenyl) propane (i.e., o, p-BPA), substituted indane, , Hydroxyphenylchroman, substituted xanthylene, and higher condensation compounds containing at least three phenyl rings in the molecular structure are present in minor amounts. Further, additional subcomponents such as anisole, mesityl oxide, mesitylene, and diacetone alcohol can be formed by the reaction of acetone with the autocondensation and impurities in the raw material.

Such byproducts as well as water, phenol and acetone may adversely affect the suitability of BPA for polymer preparation and generally must be removed by suitable processes. In particular, BPA raw materials used in the manufacture of many polycarbonates are subject to high purity requirements.

The post-treatment and purification method of BPA is carried out by cooling the reaction mixture and precipitating the BPA / phenol adduct by suspension crystallization to remove BPA in the form of approximately equimolar amounts of crystalline adducts containing phenol from the reaction mixture can do. The BPA / phenol adduct crystals can then be removed from the liquid phase by a suitable solid-liquid separation device, such as a rotary filter or centrifuge, and further purified.

The resulting adduct crystals typically have a BPA purity greater than 99% for the subcomponent and a phenolic component of about 40%. The impurities attached to the surface can be removed from the adduct crystals by washing with a suitable solution typically containing one or more components from the group comprising acetone, water, phenol, BPA and the subcomponents.

The BPA / phenol adduct crystals obtained after the suspension crystallization and solid-liquid separation of the reaction liquid described above are generally prepared by a method such as, for example, a distillation, desorption or extraction method capable of achieving phenol removal and possibly reduction in the concentration of subcomponents in BPA Followed by an additional purification step that may include.

Alternatively, phenol may also be removed from the BPA / phenol adduct crystals by a melt process.

As mentioned, there is a high requirement for the extraction of BPA / phenol adduct crystals from the product mixture. Thus, in addition to excess phenol and possibly unreacted acetone, the process is generally carried out in the presence of water and various other by-products of the bisphenol A preparation, such as the abovementioned 2- (4-hydroxyphenyl) -2- (2 Hydroxyphenyl) propane, substituted indans, hydroxyphenylindanols, hydroxyphenylchromans, spirobisindanes, substituted indanols, substituted xanthines, and more condensed compounds containing three or more phenyl rings in the molecular structure Should also be removed.

Thus, for example, EP 1268379 B1 describes a process for the production of BPA / phenol adduct crystals by crystallization. Preferably, the preparation of PBA having a purity of 99.5% by two-step crystallization, wherein the product mixture is first cooled to about 50 to 70 캜 and then cooled to 40 to 50 캜, is described.

As the purity requirements imposed on bisphenol A are always increasing, further process improvements are needed, for example in polycarbonate manufacture, to ensure increased quality requirements.

This may be possible, for example, by increasing the residence time in the crystallizer. That is, for example, from European Patent Application 1607380 A1, when the residence time in the crystallization is shorter than 0.5 hours and the crystallization is correspondingly faster, the inclusion of the reaction mixture or in other words impurities in the BPA / phenol adduct crystals It is known that poor bisphenol A quality is obtained by incorporation and that a residence time in the range of 1 to 3 hours is preferred.

Another disadvantage of the process described in EP 1268379 B1 is that in the case of such a two-stage crystallization, deposits (fouling) can occur on the surface of the circulating cooler in the first crystallization stage (high temperature stage). For example, to remove deposits by heating to about 80 ° C, the circulation cooler must be shut down at regular intervals to remove deposits by melting. The production should be stopped during this time, or the crystallization should be carried out only in the second crystallization step. This can lead to product degradation characterized by production losses and / or increased by-product (impurity) ratios in BPA.

The present invention generally relates to a process for preparing high purity bisphenols. More specifically, the present invention relates to a process for preparing bisphenols, preferably bisphenol A (BPA), having a purity of more than 99.7%.

One object of the present invention was to provide a bisphenol manufacturing method with a purity of more than 99.7% accompanied by a time lapse between shutdowns of the high temperature crystallization step to remove the deposit by melting.

One embodiment of the present invention

(a) reacting phenol and acetone in the presence of an acidic catalyst to form a bisphenol-containing product mixture;

(b) removing at least a portion of the bisphenol from the product mixture by crystallization in the form of a bisphenol / phenol adduct, filtering, and washing to provide the bisphenol / phenol adduct crystals; And

(c) removing at least a portion of the phenol from the bisphenol / phenol adduct crystals to provide a bisphenol of greater than 99.7% purity,

In this case, the crystallization includes continuous suspension crystallization, and the product mixture is first cooled in a first crystallization apparatus and a second crystallization apparatus, which are connected in parallel in the first crystallization step, to a temperature of 50 to 70 ° C, 1 and a third crystallization device connected in series downstream of the second crystallization device, wherein the total residence time in the crystallization of the product mixture exceeds 4 hours < RTI ID = 0.0 > .

In various embodiments of the process according to the present invention, the process advantageously comprises a step wherein the first crystallization step comprises at least 50 to 85% of the total crystallization volume of the two-step crystallization, and wherein the total volume of the crystallizer is two- Or more than four times the product-containing suspension to be injected into the reactor.

In various embodiments of the process according to the invention, the process advantageously comprises a first crystallization step comprising at least 60 to 80% of the total crystallization volume of the two-step crystallization, wherein the total volume of the crystallizer is in a two- And more than four times the product suspension containing the product to be injected.

In various embodiments of the process according to the invention, the process advantageously comprises the step of introducing a product-containing suspension into the crystallization, wherein the product suspension contains from 15 to 40% by weight of BPA, from 60 to 85% by weight of phenol, o, p-BPA 0 to 5 wt.% Of trisphenol, 0 to 7 wt.% Of indan / indene, 0 to 7 wt.% Of chroman / chromene, 0 to 5 wt.% Of water, 0 to 8 wt. 0 to 5% by weight of o-BPA, and 0 to 5% by weight of isopropenylphenol.

In various embodiments of the process according to the invention, the process can advantageously be carried out such that the cleansing is carried out, at least in part, by a phenol derived from the preparation of the polycarbonate by a melt process.

Another embodiment of the present invention is a compound of formula

(a) reacting phenol and acetone in the presence of an acidic catalyst to provide a mixture comprising 15 to 40 wt.% of bisphenol A, 60 to 85 wt.% of phenol, 0.5 to 7 wt.% of o, p-bisphenol A, 0 to 5% by weight of trisphenol, 0 to 7% by weight of at least one indan / indene, 0 to 7% by weight of at least one chroman / chromene, 0 to 5% from 0 to 5% by weight of o-bisphenol A, and from 0 to 5% by weight of at least one isopropenylphenol;

(b) removing at least a portion of the bisphenol A from the product mixture by crystallization in the form of a bisphenol A / phenol adduct, filtering and washing to provide the bisphenol A / phenol adduct crystals; And

(c) removing at least a portion of the phenol from the bisphenol A / phenol adduct crystals to provide greater than 99.7% purity of bisphenol A,

In this case, the crystallization includes continuous suspension crystallization, and the product mixture is first cooled in a first crystallization apparatus and a second crystallization apparatus, which are connected in parallel in the first crystallization step, to a temperature of 50 to 70 ° C, 1 and a third crystallization device connected in series downstream of the second crystallization device, wherein the total residence time in the crystallization of the product mixture exceeds 4 hours < RTI ID = 0.0 > , Wherein the total crystallization volume of the three or more crystallization apparatus is at least four times the volume of the product mixture injected into the crystallization per hour and the first crystallization step comprises at least 50 to 85% of the total crystallization volume.

The above summary and the following detailed description of the invention are better understood when read in conjunction with the appended drawings. In order to facilitate the description of the invention, representative embodiments which are considered exemplary are shown in the drawings. It should be understood, however, that the invention is not limited in its application to the exact facilities and devices illustrated.

In the drawings,

1 is a schematic flow diagram of a method according to one embodiment of the present invention,

Figure 2 is a schematic flow diagram of a comparison method.

The singular forms used herein are used interchangeably with "one or more" and "at least one" unless the context clearly dictates otherwise. Thus, for example, in the present specification and claims, "phenol" may refer to one phenol, or more than one phenol. Also, all numbers are understood to have been modified to "about" unless otherwise specified.

In various preferred embodiments of the process according to the invention, the process preferably comprises heating the liquid to be crystallized before crystallization at a temperature of less than 80 DEG C, preferably at a temperature of 75 DEG C, particularly at a temperature of from 75 DEG C to > 70 DEG C . ≪ / RTI >

The crystallization which is carried out in the process according to the invention is carried out in three or more crystallization units, which may comprise a crystallization vessel, a circulation pump and a heat exchanger, respectively. Preferably, each crystallization apparatus comprises one or more heat exchangers. Particularly preferably each crystallization apparatus comprises one heat exchanger. The product mixture produced by the reaction of phenol and acetone from which the bisphenol A / phenol adduct is precipitated is preferably incorporated into the circulation just prior to crystallization.

The total volume of all crystallization devices used is preferably at least four times the volume of the product-containing suspension (i. E., The product mixture) injected into the crystallization per hour.

The crystallization in the various embodiments of the process according to the invention is preferably carried out in two stages. In this regard, the first step includes two or more crystallization devices connected in parallel. In the first step, additional crystallization devices other than these two may be connected, and the crystallization device added in this way is connected in parallel to the remaining two. Preferably 50% or more, more preferably 55% or more, particularly preferably 60% or more of the total crystallization volume over all steps of crystallization is preferably carried out in the first crystallization step. The temperature of the first crystallization step is generally less than 70 ° C, preferably less than 65 ° C, particularly preferably about 50 to 65 ° C, very particularly preferably about 50 to 62 ° C.

In various preferred embodiments of the process according to the invention, the process is preferably carried out in such a way that the bisphenol A content of the product mixture introduced into the first crystallization step is from 15 to 40% by weight, more preferably from 15 to 35% by weight, Can be 20 to 35% by weight.

In the first crystallization step, two or more crystallization apparatuses, generally including a crystallization vessel, a cooler and a circulation pump, are operated in parallel with each other. In various preferred embodiments, the volume capacities of two or more crystallization devices in the first crystallization step are equal to each other. Preferably, the volumetric capacity of the crystallization apparatus of the first stage is greater than 20% of the volumetric capacity of the second stage, and particularly preferably, the volumetric capacity of the first stage is 1 1/2 times or more Big. In various particularly preferred embodiments, the volume capacities of all the crystallization apparatuses are equal to each other. That is, in various embodiments where the first stage includes two crystallization devices, the second stage includes one crystallization device, and the volume capacities of these three crystallization devices are equal to each other, the total volume capacity of the first stage is Is twice the volume capacity of the second stage.

In the second crystallization step, one or more crystallization devices are connected in series to the two first crystallization devices. The temperature of the second stage crystallization apparatus is lower than in the second stage, preferably less than 50 캜, particularly preferably less than 45 캜, very particularly preferably about 40 to 43 캜. Preferably, after leaving the second crystallization step comprising at least one crystallization device connected in series to the crystallization device of the first stage, the content of dissolved bisphenol A in the mother liquor from the final crystallization device of the second stage is Is 5 to 20% by weight, more preferably 5 to 15% by weight based on the total weight of the liquid mother liquor.

Thereafter, the suspension obtained from the second crystallization step is filtered, purified by a cleaning process known to those skilled in the art, and then separated into bisphenol A and phenol by a separation process known to the person skilled in the art, for example by evaporation, distillation or stripping To obtain a bisphenol A / phenol adduct. In this way, bisphenol A having a purity of more than 99.7% can be obtained by the process according to the present invention for the total amount of products excluding phenol still contained.

The process for preparing adduct crystals composed of bisphenol A and phenol according to the present invention can provide bisphenol A and phenol adducts of such high purity and therefore can be used for producing high quality secondary products such as polycarbonate, Additional post-treatment steps generally required for the production of bisphenol A suitable for resins and the like can be avoided. The additional post-treatment step generally required is, for example, an additional crystallization step or an additional distillation step.

A further advantage of the process according to the invention is that the possibility of a longer residence time in the high temperature stage leads to a reduction in the supersaturation in the crystallisation stage and thus a less frequent cleaning of the crystallization deposit in the heat exchanger It is a point.

Another advantage of the process according to the invention is that due to the parallel operation of the crystallizers in the first stage, even during the melting of one crystallizer, the other crystallizers still operate at the same temperature, . This improves system availability while increasing product purity.

A further advantage of the process according to the invention is that such a production process has a higher production capacity when the heat exchanger is already partially coated with deposited deposition deposits. Partially calcined deposits in the heat exchanger have a negative effect on heat transfer, so for a given amount of production it must be corrected by cooling water temperature drop. This accelerates the coating of the heat exchanger by re-precipitating deposits, and eventually more frequently causes the melting of the crystallizer. Using the method according to the invention, the production volume flow rate can be matched to the degree of coating of each heat exchanger when the heat exchanger is partially coated, and product quality can be maintained while maintaining a high level of production in this way .

In a preferred embodiment of the process according to the invention, the crystallization of the adduct composed of bisphenol and phenol can be carried out such that the heat exchanger (e. G., Circulation chiller) is operated with the temperature controlled hot water as the cooling medium. In this connection, it is particularly preferred that the temperature difference between the temperature-controlled hot water and the product mixture to be cooled is less than 8 K, very particularly preferably less than 5 K.

In various preferred embodiments of the process according to the present invention, the crystallization apparatus of the first stage and the peripheral equipment associated therewith are preferably cleaned by heating to more than 80 DEG C, preferably at regular time intervals of 25 to 60 days During this time, the operation of the circulation system can be carried out with the crystallization of the adduct composed of bisphenol and phenol so as to continue using another crystallization apparatus arranged in parallel in the first stage.

In various preferred embodiments of the process according to the invention, the crystallization of the adduct composed of bisphenol and phenol can be carried out as suspension crystallization, preferably in the form of cyclic crystallization.

Bisphenols other than bisphenol A can also be prepared by the process according to the invention. Therefore, it should be understood that the description of the present specification for the preparation of bisphenol A applies equally to the preparation of other bisphenols.

Unsubstituted phenol is preferably used in the process according to the present invention. Other bisphenols can be prepared by the process according to the invention using the corresponding phenol derivatives.

In various preferred embodiments of the process according to the invention, a product mixture (i. E. Suspension) comprising the following components (wt.% Is based on the total weight of the suspension) is injected into the crystallization.

15 to 40% by weight, preferably 15 to 35% by weight, more preferably 20 to 35% by weight of BPA;

Phenol: 60 to 85% by weight, preferably 65 to 85% by weight, more preferably 65 to 80% by weight;

o, p-BPA: 0.5 to 7% by weight, preferably 1 to 6% by weight, more preferably 1 to 5% by weight;

Trisphenol: 0 to 5% by weight, preferably 0 to 3% by weight;

Indan / indene: 0 to 7% by weight, preferably 0 to 5% by weight;

Chroman / chromene: 0 to 7% by weight, preferably 0 to 5% by weight;

Water: 0 to 5% by weight, preferably 0 to 3% by weight;

Acetone: 0 to 8% by weight, preferably 0 to 5% by weight, more preferably 0 to 2% by weight;

o, o-BPA: 0 to 5% by weight, preferably 0 to 3% by weight;

Isopropenylphenol: 0 to 5% by weight, preferably 0 to 3% by weight.

Optionally, the water, unreacted acetone and other low boiling compounds contained in the product mixture can be completely or partially removed by distillation, preferably by vacuum distillation, prior to suspension crystallization.

Mixed bisphenol A / phenol crystals (bisphenol A / phenol adduct) can be separated from the mother liquor using a filtration medium suitable for solids removal. Desirably, cleaning of the removed solids is also possible in such an apparatus. This is carried out, for example, on a rotatable filter, a belt filter and a (vacuum) disk filter as well as a suitable centrifuge such as a skimmer centrifuge, a screen-conveyor centrifuge, or a push-type centrifuge can do. Preferably, a pressurized rotary filter, particularly preferably a rotary vacuum filter, is used.

Cleaning of the removed solids (filter cake) may also be performed separately in suitable devices after solid-liquid separation.

The filter cake of mixed bisphenol A / phenol crystals can be cleaned with fresh phenol, and / or phenol re-fed in the bisphenol A manufacturing process, which is pre-purified by distillation. The cleaning is preferably carried out at a phenol temperature of 40 to 70 占 폚.

The phenol accumulated in the production of the polycarbonate by the melting process may be used for cleaning.

The washed mixed crystals are then preferably melted and the phenol is removed from the resulting melt as is known in the art. Preferably, the two step process removes the phenol of the melt and other readily volatilized impurities. In this case, the melt is treated in both a first stage with both vacuum and elevated temperature and in a second stage with a desorption gas, preferably nitrogen, at a temperature of 160 to 210 ° C, Lt; / RTI >

In another preferred embodiment, the phenol can be removed in only one step at elevated temperature and vacuum, in which a phenol residue content in the bisphenol of less than or equal to 10% by weight based on the total amount of product can be established.

The bisphenol A prepared by the process according to the present invention can be reacted with phosgene by an interfacial process or reacted with a diaryl carbonate, preferably diphenyl carbonate, by a melting process to form a polycarbonate can do. The BPA produced by the process according to the invention can also be used as starting materials for the preparation of various polymeric substances such as polyacrylates, polyetherimides, modified phenol formaldehyde resins and epoxy resins.

The invention will now be further described with reference to the following non-limiting examples.

Example

Example 1 (Present invention)

In FIG. 1, the reaction mixture from BPA manufacture (R) was injected into suspension crystallization in an apparatus comprising three crystallization apparatuses (K1, K2 and K3 in FIG. 1) for post-BPA treatment and purification. For this purpose, two-stage crystallization, which starts at 54 ° C in the first stage and continues at 41 ° C in the second stage, is carried out. The first stage comprises two crystallization devices K1 and K2 operated in parallel, The second stage included one crystallization device (K3) having a volume of 80% of the total of the first stage crystallization devices K1 and K2. The reaction liquid to be crystallized had a bisphenol A content of 30%. The reaction mixture was added to the circulating stream immediately upstream of crystallization apparatus K1 and K2 at 70 占 폚.

The circulation chiller was fed from the top to the bottom of the chiller, and the chiller was operated with hot water with controlled temperature. The maximum temperature difference between the temperature controlled hot water and the cooled suspension was 3K.

The prepared mixed crystal suspension was removed from the crystallizer K3 after a crystallization residence time of 8.5 hours.

For this procedure, a tube-bank heat exchanger was used as the heat exchanger. No disturbance of heat transfer due to deposits on the inner surface of the cooling tube was observed within a 3-month time interval, so that during this time interval it is necessary to remove the BPA coating and the BPA / phenol coating from the inner surface of the cooling tube There was no.

By this type of crystallization, high purity bisphenol A / phenol adduct crystals were obtained.

After filtration (F) and phenol separation (PhT), bisphenol A (BPA) with a purity of 99.75% and a hazen color index of about 15 was obtained. The haze color index was visually compared with the APHA standard colorimetric solution according to ASTM D 1209-97.

Example 2 (Invention)

In FIG. 1, the reaction mixture from BPA manufacture (R) was injected into suspension crystallization in an apparatus comprising three crystallization apparatuses (K1, K2 and K3 in FIG. 1) for post-BPA treatment and purification. For this purpose, two-stage crystallization, which starts at 54 ° C in the first stage and continues at 41 ° C in the second stage, is carried out. The first stage comprises two crystallization devices K1 and K2 operated in parallel, The second stage included one crystallization apparatus (K3) having a volume of 50% of the sum of the first stage crystallization apparatuses K1 and K2. The reaction liquid to be crystallized had a bisphenol A content of 30%. The reaction mixture was added to the circulating stream immediately upstream of crystallization apparatus K1 and K2 at 70 占 폚.

The circulating flow of the cyclic crystallization was injected into the lower portion of each crystallization vessel and removed from the upper center of each crystallization vessel.

The circulation chiller was fed from the top to the bottom of the chiller, and the chiller was operated with hot water with controlled temperature. The maximum temperature difference between the temperature controlled hot water and the cooled suspension was 3K.

The prepared mixed crystal suspension was removed from the crystallizer K3 after a crystallization residence time of 8.5 hours.

For this procedure, the tube-bank heat exchanger was used as a heat exchanger. No disturbance of heat transfer due to deposits on the inner surface of the cooling tube was observed within a time interval of 10 months and as a result there was no need to remove the BPA coating and the BPA / phenol coating on the inner surface of the cooling tube during this period .

After filtration (F) and phenol separation (PhT), bisphenol A (BPA) having a purity of 99.79% and a Hazen color index of less than 15 was obtained. The haze color index was visually compared with the APHA standard colorimetric solution according to ASTM D 1209-97.

High purity bisphenol A / phenol adduct crystals were obtained by crystallization of this type according to the present invention. By selecting the volume of the crystallization apparatus in the second step, the purity can be further increased as compared with Example 1.

Example 3 (Comparative Example)

In FIG. 2, the reaction mixture from BPA manufacture (R) was injected into the suspension crystallization in an apparatus comprising two crystallization apparatus (K1 and K2 in FIG. 2) for post-BPA treatment and purification. For this, a two-stage crystallization was carried out, starting at 54 ° C in the first stage and continuing at 41 ° C in the second stage, and the crystallization volumes of the two crystallization apparatuses (K1 and K2) were the same. The reaction liquid to be crystallized had a bisphenol A content of 30%. The reaction mixture was added to the circulation stream immediately upstream of the crystallization apparatus K1 at 70 占 폚.

The circulating flow of the cyclic crystallization was injected into the lower portion of each crystallization vessel and removed from the upper center of each crystallization vessel.

The circulation chiller was fed from the top to the bottom of the chiller, and the chiller was operated with hot water with controlled temperature. The maximum temperature difference between the temperature controlled hot water and the cooled suspension was 3K.

The prepared mixed crystal suspension was removed from K2 after a crystallizer residence time of 8.5 hours.

For this procedure, the tube-bank heat exchanger was used as a heat exchanger. In order to remove the BPA coating and the BPA / phenol coating from them, the inner surface of the cooling tube was quickly heated to about 80 DEG C at about two months intervals, or the circulation system was continuously operated while heating the contained product, The crystallizer system had to be cleaned.

After filtration (F) and phenol separation (PhT) from the bisphenol A / phenol adduct crystals obtained in this manner, bisphenol A (BPA) having a purity of 99.72% and a Hazen color index of 20 was obtained. The haze color index was visually compared with the APHA standard colorimetric solution according to ASTM D 1209-97.

Those skilled in the art will appreciate that modifications can be made to the embodiments described above without departing from the broad idea of the invention. Accordingly, the invention is not to be limited to the specific embodiments disclosed, but includes modifications within the spirit and scope of the invention as defined by the claims.

1 schematically illustrates an embodiment according to the invention in which three crystallization devices K1, K2 and K3 are used, the former two of which (K1 and K2) operate in parallel and the third (K3) are connected in series with the two preceding ones.

Fig. 2 shows a method of using only two crystallization devices K1 and K2 connected in series.

Description of the Related Art

R: Reaction vessel or reactor where the production of bisphenol A is carried out

E: feed for bisphenol A preparation

K1: Crystallization apparatus 1 (shortly referred to as crystallizer 1)

K2: crystallization apparatus 2 (also referred to as crystallizer 2 for short)

K3: Crystallization apparatus 3 (also referred to as crystallizer 3 for short)

F: Filtration

PhT: phenol separation

Ph: phenol

BPA: bisphenol A

Claims (18)

(a) reacting phenol and acetone in the presence of an acidic catalyst to form a product mixture comprising bisphenol A; (b) removing at least a portion of the bisphenol A from the product mixture by crystallization in the form of a bisphenol A / phenol adduct, filtering and washing to provide the bisphenol A / phenol adduct crystals; And (c) removing at least a portion of the phenol from the bisphenol A / phenol adduct crystals to provide greater than 99.7% purity of bisphenol A, In this case, the crystallization includes continuous suspension crystallization, and the product mixture is first cooled in a first crystallization apparatus and a second crystallization apparatus, which are connected in parallel in the first crystallization step, to a temperature of 50 to 70 ° C, 1 and a third crystallization device connected in series downstream of the second crystallization device, wherein the total residence time in the crystallization of the product mixture exceeds 4 hours < RTI ID = 0.0 > ≪ / RTI > The process according to claim 1, wherein the product mixture is cooled to a temperature of less than 80 캜 before the first crystallization step. The method of claim 1, wherein each of the three or more crystallization apparatuses comprises a heat exchanger having a cooling medium, wherein the temperature difference between the cooling medium and the product mixture to be cooled is less than 8 ° K. The method of claim 1, wherein the total crystallization volume of the three or more crystallization apparatus is at least four times the volume of the product mixture injected into the crystallization per hour, and the first crystallization step comprises at least 50 to 85% of the total crystallization volume . 5. The process according to claim 4, wherein the product mixture is cooled to a temperature of less than 80 DEG C before the first crystallization step. 6. The method of claim 5, wherein each of the three or more crystallization apparatuses comprises a heat exchanger having a cooling medium, wherein the temperature difference between the cooling medium and the product mixture to be cooled is less than 8 DEG K. The process according to claim 1, wherein the total crystallization volume of the three or more crystallization apparatuses is at least four times the volume of the product mixture injected into the crystallization per hour and the first crystallization step comprises at least 60 to 80% . The process of claim 1, wherein the product mixture injected into the crystallization is selected from the group consisting of 15-40 wt.% Bisphenol A, 60-85 wt.% Phenol, 0.5-7 wt.% O, p-bisphenol A, 0 to 5% by weight of trisphenol, 0 to 7% by weight of at least one indan / indene, 0 to 7% by weight of at least one chroman / chromene, 0 to 5% by weight of water, 0 to 8% 0 to 5% by weight o-bisphenol A, and 0 to 5% by weight of at least one isopropenyl phenol. A process according to claim 8, wherein the total crystallization volume of the three or more crystallization apparatuses is at least four times the volume of the product mixture injected into the crystallization per hour and the first crystallization step comprises at least 50 to 85% of the total crystallization volume . The process according to claim 9, wherein the product mixture is cooled to a temperature below 80 캜 before the first crystallization step. 11. The method of claim 10 wherein each of the three or more crystallization apparatuses comprises a heat exchanger having a cooling medium and wherein the temperature difference between the cooling medium and the product mixture to be cooled is less than 8 [ The process according to claim 1, wherein the cleaning is carried out with phenol, wherein at least a portion of the phenol is obtained from the melt manufacture of polycarbonate. (a) reacting phenol and acetone in the presence of an acidic catalyst to provide a mixture comprising 15 to 40 wt.% of bisphenol A, 60 to 85 wt.% of phenol, 0.5 to 7 wt.% of o, p-bisphenol A, 0 to 5% by weight of trisphenol, 0 to 7% by weight of at least one indan / indene, 0 to 7% by weight of at least one chroman / chromene, 0 to 5% from 0 to 5% by weight of o-bisphenol A, and from 0 to 5% by weight of at least one isopropenylphenol; (b) removing at least a portion of the bisphenol A from the product mixture by crystallization in the form of a bisphenol A / phenol adduct, filtering and washing to provide the bisphenol A / phenol adduct crystals; And (c) removing at least a portion of the phenol from the bisphenol A / phenol adduct crystals to provide greater than 99.7% purity of bisphenol A, In this case, the crystallization includes continuous suspension crystallization, and the product mixture is first cooled in a first crystallization apparatus and a second crystallization apparatus, which are connected in parallel in the first crystallization step, to a temperature of 50 to 70 ° C, 1 and a third crystallization device connected in series downstream of the second crystallization device, wherein the total residence time in the crystallization of the product mixture exceeds 4 hours < RTI ID = 0.0 > , Wherein the total crystallization volume of the three or more crystallization apparatuses is at least four times the volume of the product mixture injected into the crystallization per hour, and the first crystallization step comprises at least 50 to 85% of the total crystallization volume . 14. The process according to claim 13, wherein the product mixture is cooled to a temperature below 80 < 0 > C before the first crystallization step. 15. The method of claim 14, wherein each of the three or more crystallization apparatuses comprises a heat exchanger having a cooling medium, wherein the temperature difference between the cooling medium and the product mixture to be cooled is less than 8 [ delete delete delete

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